A lamp of the general type to which the present invention relates is shown and described in the referenced application Ser. No. 07/694,465, filed May 1, 1991, Schoenherr et al, assigned to the assignee of the present application. The lamp is a single-based high-pressure discharge lamp, particularly suitable for use in automotive headlights. The discharge vessel of the lamp is formed with an essentially cylindrical extension, which may be hollow, that is, tubular. The extension is melt-seated in the base by using a high-frequency responsive material within the plastic material. Upon application of an electrical high-frequency field, the plastic material surrounding the extension will melt and securely retain the discharge vessel in position in the plastic base. An adhesive and melt connection will thus be formed between the glass of the vessel and the plastic of the base.
It has been found that, in extended operation of the lamp, the base may deteriorate. As the plastic material ages, it has a tendency to shrink and lose material by vaporization. This change in the plastic base may interfere with reliable retention of the discharge vessel in the base. Since the discharge vessel must be accurately aligned within the base, so that, when the base is fitted into an optical system, for example a reflector, the discharge will take place at a defined position with respect to the optical system, it is important that the accurately positioned location of the lamp with respect to the base be retained over the entire operating lifetime of the discharge vessel itself. The danger arises that material from the base which vaporizes may deposit on the optical system, for example on the surface of a reflector, to form precipitates thereon, leading to premature loss of light and dulling of the reflector surface.